This invention relates to hydrofoils for boats and, more particularly, to a hydrofoil adapted for attachment to the lower unit of a marine outboard engine or marine outdrive, which increases the stability of a boat driven at higher speeds by the lower unit including such assembly while improving the acceleration performance of the boat.
Marine hydrofoils are commonly used on boats and ships to increase performance and especially to allow operation at high speeds. Typical arrangements include combinations of bow and stern hydrofoils which act as struts to lift the main hull of the boat or ship from the water as power is increased thereby allowing operation at significantly higher speeds.
More recently, the use of stabilizer fins at the rear of smaller boats such as sport runabouts or high speed fishing boats known as "bass boats" have become popular. Exemplary of such structures which are added to alter the high speed running attitude of the associated boats are Kohler U.S. Pat. No. 4,744,779, Happel U.S. Pat. No. 4,738,644, Larson U.S. Pat. No. 4,487,152 and Loch U.S. Pat. No. 4,445,452. Each of these patents discloses stabilizing fins or hydrofoils extending generally horizontally outwardly or downwardly from either side of a propulsion unit at the rear of a small craft. Such stabilizers are intended to help force the bow of the boat downwardly during acceleration to improve visibility and reduce "porpoising" of the boat at higher speeds thereby providing more stability. However, in use, various drawbacks with these prior known stabilizers have been revealed.
First, since prior stabilizers have been positioned immediately adjacent the propeller on the propulsion unit, they have tended to reduce boat speed at both normal crusing and high power settings because of the inherent drag caused by continued contact with the water by the substantially horizontally extending elements. Secondly, these stabilizers have often struck obstructions at or slightly below the surface of the water causing damage not only to the stabilizers themselves but also to the propulsion unit. For example, should a boat including the prior stabilizers run up on a sand bar unexpectedly, the stabilizers will dig in and break or dismember the lower unit. In some cases, such stabilizers have also induced forwardly extending spray over the transom of the craft at certain trim angles causing discomfort to the occupants or the boat. Further, since modern day small craft often include V-shaped hull bottoms and are often lifted from the water at marinas using elongated fork lifts for storage in vertically stacked arrangements, such horizontally extending fins have tended to obstruct access to the rear of the boat and the hull with fork lifts making launching and retrieval difficult.
The present invention was conceived to provide improved performance and overcome such operational drawbacks encountered with prior known stabilizers for smaller watercraft.